The document discusses several topics related to percentages including reverse percentages, profit and loss, discounts, goods and services tax, and commission. Some key points include: 1) A word problem about finding the percentage increase or decrease in the cost of a pool given changes in raw material, overhead, and wage costs. 2) A profit calculation expressed as a percentage of selling price for a fruit seller who mixes different types of pears. 3) Questions about calculating the marked price and determining the sale price of an air conditioner after successive discounts. 4) A calculation of service charge and GST for a seafood rice order with a discount. 5) Commission calculations for a property agent based on a percentage

1. Reverse
percentage,
Profit, Loss
and Discount
Bambini Junior High School
7th Grade / Khaerunnisa

2. Reverse percentage and Profit and
Loss
1. The production cost of a pool consist of the raw materials at $1200, the cost of
overheads at $310 and wages at $250. if the cost of raw materials and
overheads are increased by 8% and 12% respectively, while wages decrease by
18%. Find the percentage of icrease or decrease in the cost of pool?
2. A fruit seller mixes 4 kg of pears which cost $5 per kg, with 3 kg of pears of
pears which cost $4 per kg. He sells the mixture at $3 per 250 g. Express the
profit as a percentage of his selling price.

3. Discount
1. An air conditioner is sold $700 after a discount of 12.5%.
• Find the marked price of the air conditioner
• If a 10% discount is given in the marked price of the air conditioner before
it is sold at a futher discount of 2.5%, would the sale price still be $700?
Show your

4. Goods and Services Tax
1. Farhan orders one plate of seafood fried rice at a restaurant which offers 25%
discount. The marked price of the seafood fried rice is $9.50. given that there
is a service charge of 10% and GST 7%, find
i. The amount of service charge he has to pay
ii. The amount of GST he has to pay
iii. The total bill

5. Comission
1. A property agent charges a comission of 2.5% on the selling price of a house.
i. Given that the agent sells a house for $650 000, find the amount of
comission he receives
ii. On another occasion, he receives a commission of $12 000. Find the
selling price of the house.
2. Lixin’s monthly income consists of a basic salary $500 and a comission of a 4%
on her sales for the month. If her income is $1220 for a particular month, find
her sales for that month

6. Rates Speed Point, lines
and planes
Angles

7. Shop A
6 eggs cost $1.50
Shop B
12 eggs cost $2.40
Shop A sells eggs at $1.50 per
half dozen whereas Shop B selss
eggs of the same size and quality
at $2.40 per dozen. Which shop
would you buy the eggs from?
Find which shop sells the eggs cheaper
Shop A
6 eggs cost $1.50
Shop B
12 eggs cost $2.40
1 egg costs
$1.50
6
= $0.25 = 25₵ 1 egg costs
$2.40
12
= $0.20 = 20₵

8. 1. Jun Wei borrows $1000 from a financial institution at a simple
interest rate of 4% per annum. Calculate the amount of interest
payable at the of 3 years
The amount of simple interest which Jun Wei has to pay at
the end of 1 year is
4% of $1000 = 1
year
The amount of simple interest which Jun Wei has to pay for
3 years
$40 x 3 = $120
4
100
× $1000 = $40

9. Farrel invests $4000 in a savings scheme that pays 2% simple interest
per annum. If he wish to buy a motorcycle which cost $4480. calculate
the time taken for his investment to reach $4480
Amount of interest Farrel earns = $4480 - $4000 = $480
2% of $4000
Time taken =
=
$480
$80
= 6
Interest per year
2
100
× $4000 =
Time taken for his investment to grow to $4480 = 6 years
$80
𝒂𝒎𝒐𝒖𝒏𝒕 𝒐𝒇 𝒊𝒏𝒕𝒆𝒓𝒆𝒔𝒕 𝒆𝒂𝒓𝒏𝒆𝒅
𝒊𝒏𝒕𝒆𝒓𝒆𝒔𝒕 𝒑𝒆𝒓 𝒚𝒆𝒂𝒓

10. Total reliefs = $3000 + $4000+ $2000 + $16 800 + $940 = $34 740
$49 260
Chargeable income = $84 000 - $34 740 = $49 260
𝑓𝑖𝑟𝑠𝑡 $40 000 ∶ $550
Income tax payable = $550 + $ 648.20 = $1198.20
Next $9260 at 7% :
7
100
× $9260 = $ 648.20
In 2012, Mr. Lee earned annual income pf $84 000, the amount that will be subjected to income
tax is:
• Personal relief of $3000 - Wife relief of $2000
• $4000 relief for each of his 3 children - Donations charitable organisations of $940
• CPF contribution of $16800
For the remaining income that will be taxed, the gross tax payable for the first $40 000 of his
chargeable income is $550 and the tax rate for the rest of his chargeable income is 7%. Find his
income tax payable

11. Quiz
1. 200 g of ferteliser is required for a plot of land that has an area of 8 m2. Find:
i. The amount of ferteliser needed for a plot of land that has an area of 14 m2.
ii. The area of land that can be fertelised by 450 g of ferteliser
2. Rui feng invests $16 800 in a saving plan that pays 5% simple interest per annum. Find
the time taken for his investment to reach $18 900
3. In 2012, Mr Goh earned a gross annual income o f $185 000, the total amount that will
not be subjected to income tax is :
• Personal relief $3000
• $4000 relie for his child
• $5000 relief for each of his parents
• CPF contribution of $18 600
For the remaining income that will be taxed, the gross tax payable for the first $120 000
of his chargeable income is $7950 and the tax rate for his chargeable income is 15%. Find
his income tax payable

12. The distance from the southern tip of singapore to
batam is 20 km. If a ferry starts its journey from
Singapore to 10.50 a.m. and reaches Batam at 11.30
a.m., calculate the speed of the ferry in
a. Km/h b. m/s
10.50 a.m.
a. 40 min =
40
60
=
2
3
ℎ𝑜𝑢𝑟
𝑠𝑝𝑒𝑒𝑑 𝑜𝑓 𝑓𝑒𝑟𝑟𝑦 =
𝑑𝑖𝑠𝑡𝑎𝑛𝑐𝑒 𝑡𝑟𝑎𝑣𝑒𝑙𝑙𝑒𝑑
𝑡𝑖𝑚𝑒 𝑡𝑎𝑘𝑒𝑛
b. 20 km = 20 x 1000 = 20 000 m
=
20
2
3
= 20 ×
3
2
= 30 𝑘𝑚/ℎ𝑟
11.30 a.m.
40 minutes
40 minutes = 40x 60 = 2400 s
𝑠𝑝𝑒𝑒𝑑 𝑜𝑓 𝑓𝑒𝑟𝑟𝑦 =
𝑑𝑖𝑠𝑡𝑎𝑛𝑐𝑒 𝑡𝑟𝑎𝑣𝑒𝑙𝑙𝑒𝑑
𝑡𝑖𝑚𝑒 𝑡𝑎𝑘𝑒𝑛
𝑠𝑝𝑒𝑒𝑑 𝑜𝑓 𝑓𝑒𝑟𝑟𝑦 =
20 000
2400
𝑠𝑝𝑒𝑒𝑑 𝑜𝑓 𝑓𝑒𝑟𝑟𝑦 = 8
1
3
𝑚/𝑠

13. Priya sets off her home on a 70 km journey for her
friends house. She travels the first 40 km of her
journey at an average speed of 40 km/h and the
remaining at an average speed of 60km/h. Calculate
the average speed for her entire journey.
Time taken for the first part of the journey =
40
40
= 1 hour .
Time taken for the second part of the journey =
70−40
60
=
1
2
ℎ
𝑇𝑜𝑡𝑎𝑙 𝑡𝑖𝑚𝑒 𝑡𝑎𝑘𝑒𝑛 = 1 +
1
2
= 1
1
2
ℎ𝑜𝑢𝑟
𝑎𝑣𝑒𝑟𝑎𝑔𝑒 𝑠𝑝𝑒𝑒𝑑 =
𝑇𝑜𝑡𝑎𝑙 𝑑𝑖𝑠𝑡𝑎𝑛𝑐𝑒 𝑡𝑟𝑎𝑣𝑒𝑙𝑙𝑒𝑑
𝑇𝑜𝑡𝑎𝑙 𝑡𝑖𝑚𝑒 𝑡𝑎𝑘𝑒𝑛
𝑎𝑣𝑒𝑟𝑎𝑔𝑒 𝑠𝑝𝑒𝑒𝑑 =
70
1
1
2
= 46
2
3
𝑘𝑚/ℎ